Hot melt applicator

ABSTRACT

The invention relates to a hot-melt adhesive applicator having a manually handleable applicator unit which is adapted to electrically heat a replaceably insertable adhesive container, in particular for adhesive which can be liquefied by the action of heat, and which has a heating unit of a material of a predetermined heat capacity and which is provided for transferring heat to the adhesive container and which affords a contact surface for the heat transfer and which has an electrical heating element, and a support module which is adapted to act on the heating element with an electrical voltage in a fitted holding condition of the applicator unit, the support module being so designed that the heating element is supplied with voltage only in the holding condition and the supply of voltage to the heating element cannot occur when the applicator unit is in an adhesive application condition of being detached from the support module.

BACKGROUND OF THE INVENTION

The present invention concerns a hot-melt adhesive applicator, inparticular a hot-melt adhesive applicator in gun form. Devices of thatkind with mains voltage-operated heating units in a manually actuablegun housing provided with an advance unit for solid adhesive bars to beheated (therefore often also referred to as a ‘heating adhesiveapplicator’) have long been known from the state of the art, but theysuffer from a series of disadvantages: thus the voltage connection whichis permanently necessary, for example by means of a mains cable, givesrise to difficulty in terms of free handling of the adhesive gun,conventional adhesives to be melted in solid bar form are limited inrespect of their range of uses, and in particular simultaneous heatingof the adhesive which is to be caused to melt for use thereof is ofteninadequate, by virtue of the structural implementations of the knownheating device.

A hot-melt adhesive applicator is known from WO 89/10324.

In addition EP 0 385 235 A1 describes a hot-melt adhesive applicator inthe form of a hot-melt adhesive applicator which is designed in theshape of a gun and which, for heating a hot-melt adhesive bar, has aplurality of separately operable heating elements in the form of PCTresistors, operation of the heating elements being effected independence on a temperature regulating circuit. A plurality of heatingelements are also described in the hot-melt adhesive applicator knownfrom DE 33 16 863 A1, in which case also an adhesive bar, under suitableactuation, can be liquefied.

Therefore the object of the present invention is to make a knownhot-melt adhesive applicator more flexible in terms of its handling anduse options, and in particular also to make it suitable for adhesives ofthe most widely varying kinds and with varying melting properties, andin addition to improve the electrical safety of known devices.

SUMMARY OF THE INVENTION

The foregoing object is attained by the hot-melt adhesive applicatorcomprising a hot-melt adhesive applicator comprising a manuallyhandleable applicator unit which is adapted for electrically heating areplaceably insertable adhesive container, in particular for adhesivewhich can be liquefied by the action of heat, and which has a heatingunit comprising a material of a predetermined heat capacity, which isprovided for the transfer of heat to the adhesive container and whichaffords a contact surface for heat transfer and which has an electricalheating element, and a support module which is adapted to act on theheating element with an electrical voltage in a fitted holding conditionof the applicator unit and which is so designed that the heating elementcan be supplied with voltage only in the holding condition and not in anoperative adhesive application condition of the applicator unit of beingdetached from the support module. The method of the present inventioncomprises the steps of claim 9.

Thus, in an advantageous manner in accordance with the invention, theapplicator unit which can be detached from the support module permitscompletely cable-free or connection-free handling of the heating modulewhich is preferably provided with a pistol-like grip, so that not onlyis it possible to reach locations which involve a difficult access, butit is also possible to avoid potential risks arising due to the presenceof an electrical power supply cable at the location of use.

The fact that the handle or grip unit is releasable in a furtherdevelopment of the invention also permits easy replacement of consumedadhesive containers which in a further preferred feature can be presentin cartridge form and, by virtue of the structural configuration of theheating unit, in the form of a profile member, can be provided withoptimised efficient input of heat. The coding of adhesive cartridges andheating module, which is provided in accordance with a development ofthe invention, permits in a particularly advantageous manner a furtherenhancement in the flexibility of the options of use involved, by virtueof a specific design configuration or setting of heating modules forspecific adhesives, in particular in regard to any, especially requiredmelting and operating temperatures, without the possibility of incorrectassociations in practical alternate operation.

The temperature switch which is provided in accordance with a furtherdevelopments permit activation or deactivation of the heating unit independence on an actual (observed) temperature so that by specificallyand targetedly switching on additional heating power at measuredtemperatures below an operating temperature it is possible to minimisedetrimental delays due to long heating times.

The brightness control unit which is provided in accordance with adevelopment of the invention also eliminates the disadvantageousconsequences of devices which are kept in a heating mode of operationover a long period of time (that is to say for example overnight), bothin regard to a worsening quality of adhesive and also in terms ofelectrical power consumption.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features and details of the invention will beapparent from the following description of preferred embodiments andwith reference to the Figures in which:

FIG. 1 is an exploded view of the present hot-melt adhesive applicatorin accordance with a first preferred embodiment with the essentialmechanical components and the co-operation thereof with each other inthe assembled condition,

FIG. 2 shows a profile view of the heating unit in the form of a metalprofile member of the embodiment of FIG. 1,

FIG. 3 shows a detail view of the heating unit of FIG. 2, and

FIG. 4 shows a side view of the heating unit of FIGS. 2 and 3.

FIG. 1 is an exploded view showing the mechanical structuralconfiguration of the hot-melt adhesive applicator according to theinvention in accordance with a first preferred embodiment.

DETAILED DESCRIPTION

A support unit 10 comprising a support bottom plate 12 and a supporthousing 14 has a mains feed line (not shown) and connecting electronicswhich by means of a pair of contacts 16 provides operating voltage for agun-shaped applicator or adhesive unit 18.

The adhesive unit 18 is formed on the one hand from a grip or handlewhich is made from grip casing portions 20, 22 and which can bereleasably connected by means of a bayonet locking unit 24 (20, 24constituting a grip unit) to a heating housing 26 comprising housingshell portions 28, 30. The heating housing 26 encloses a heating profilemember formed from aluminum (FIGS. 2 through 4) of a length 1 of about80 mm, which affords a cylindrical internal space for accommodating acylindrical adhesive container 34, for example with liquid adhesive oradhesive which can be liquefied by virtue of the external effect ofheat, and which accommodates additional PTC heating elements.

The arrangement consisting of the heating profile member 32 and thecartridge 34 is fixed in the heating housing 26 by means of rear (36)and front (38) holding rings made from heat-resistant plastic material,wherein the cartridge 34 is exposed at its exit end and has an outlet40.

Discharge of adhesive material which has been heated by means of theheating profile member 32 from the cartridge is effected by the pressureaction of an advance bar 42 which can be moved in the axial direction ofthe cartridge 34 by an advance unit formed by an advance lever 34 and anadvance hook 46, engaging a tooth arrangement of the advance bar whichis in the form of a toothed rack, as soon as an operator using his indexfinger actuates the advance lever 44 in the fashion of a gun trigger. Abraking element 48 in the form of a clip prevents the advance bar 42from moving out of the assembly in the opposite direction to thepressing direction.

Provided in the left-hand grip or housing shell portion 20 there is alsoan accommodating space 50 for a thermal or bimetal switch (not shown)which in the assembled condition contacts the heating profile portion 32at the periphery thereof and thus permits temperature measurement; thatelectrical unit produces a control signal which controls the heatingoperation of the arrangement in the manner to be described hereinafter.

As indicated in the enlarged view of a part of the arrangement as shownin FIG. 3 the heating profile member in the cross-sectional directionhas a chamber portion adapted for the insertion of two PTC heatingelements together with contacting means. To put that more precisely, afirst PTC 52 is so held in the accommodating space as shown in FIG. 3that it can be acted upon with electrical voltage through contactsengaging at the end a first conductor segment 54 and a second commonconductor segment 56. The arrangement is surrounded by an electricallyinsulating sheath 57. In the axial direction of the heating profilemember a second PTC (not shown) is disposed in aligned adjacentrelationship with the first one and is contacted with the common secondconductor segment 56 at which for example common neutral conductorpotential is applied. In contrast the first conductor segment 54 (phase)is separated for the first PTC (shown in the Figure) and the second PTC(not shown) so that in that respect it is possible to provide for acontacting action which is separate (each respectively engaging an endposition). That takes place as follows: the first PTC is adapted forongoing heating operation and with a heating temperature of about 170°C. permits continuous heating of the heating profile member to aconstant temperature of between about 130 and approximately 140° C.,which in the present embodiment is selected as the operating adhesiontemperature for the adhesive in the adhesive cartridge 34. The secondPTC is only provided for heating-up purposes, it has a higher heatingtemperature of for example 300° C. and is only activated if thetemperature of the heating unit 32, which is detected by means of thethermoelement in the accommodating space 50, is below the referenceoperating temperature of between 130 and 140° C. In that case, atroublesome waiting time until the operating temperature is regained canbe shortened by the high power which is applied for a short period oftime. In addition a red or green LED 58, 60 display those operatingconditions (that is to say current operating temperature below referenceoperating temperature or at same) in such a fashion that the situationis optically visible to the user.

In practical operation therefore the user will leave the adhesiveapplicator unit 18 in the support until, after the arrangement iselectrically switched on, the reference temperature is reached (which isattained after a heating time which is shortened in comparison with thestate of the art, by virtue of the additional powerful PTC), whereuponthen the applicator unit 18 can be removed and adhesive can bedischarged therefrom at the location of use by actuation of the lever44. After use, the applicator unit 18 is returned to the support againand, if the current temperature of the adhesive in the cartridge hasfallen below a predetermined limit value, the additional PTC isactivated again to provide an accelerated heating effect.

An embodiment which is particularly useful in practical use is one inwhich it is possible to provide for individualisation and replaceabilityof the heating device for various adhesives and cartridges, by means ofsuitable coloration of the heating housing 26 (for example coloring ofthe housing shell portions 28, 30), with a color which is characteristicof a specific adhesive in the cartridge 34: thus for example for givenadhesives which require a specific temperature operating range, aheating profile member 32 which is especially designed for that purposecan be accommodated in a housing which is characteristically coded incolor and which in terms of its coloration corresponds to the cartridgewith that adhesive so that there is no possibility of improperassociations therebetween. The operator can adapt and replace arespective color cartridge and associated heating housing for variousadhesive application uses.

What is claimed is:
 1. A hot-melt adhesive applicator comprising: anapplicator unit including a heating unit for receiving a replacablyinsertable adhesive container, said heating unit being formed of amaterial for transferring heat to the adhesive container, said heatingunit comprises a one-piece metal profile element which has a first spacefor accommodating the adhesive container and an additional space forreceiving an electrical heating element means; and a support moduleincluding means for removably connecting the applicator unit, saidsupport module further including means for selectively applying anelectrical voltage to the heating element wherein the heating elementmeans is supplied with electrical voltage when the applicator unit isconnected to the support module and not supplied when detachedtherefrom.
 2. An applicator according to claim 1, wherein the applicatorunit comprises a grip unit which is releasably connected to a heatingmodule by connecting means.
 3. An applicator according to claim 2,wherein the connecting means comprises a bayonet locking arrangement. 4.An applicator according to claim 2, wherein the grip unit includes anactuable expulsion and metering unit for expelling adhesive from theadhesive container.
 5. An applicator according to claim 1, wherein theelectrical heating element means comprises a plurality of independentlyoperated heating elements each having different electrical heatingoutputs.
 6. An applicator according to claim 1, wherein the heating unitincludes means for displacing temperature.
 7. An applicator according toclaim 1, further including an ambient brightness detection unit fordeactivating the heating element means in response to ambientbrightness.
 8. An applicator according to claim 1, wherein the adhesivecontainer is coded for each adhesive contained therein.
 9. A method foroperating a hot-melt adhesive applicator having a plurality of heatingelements for heating a heating module containing an adhesive container,comprising the steps of: electrically operating plurality of electricalheating elements of the heating module to electrically heat the adhesivecontainer; partially deactivating operation of the electrical heatingelements by selective operation of the plurality of electrical heatingelements, wherein a detected operating temperature of the adhesivecontainer exceeds a first predetermined threshold value; and renewedactivation of the electrical operation of the plurality of heatingelements as soon as the detected temperature falls below a predeterminedsecond threshold value which is lower than the first threshold value.10. A method according to claim 9 further comprising the step of:optically displaying the detected temperature and the operationalcondition of the plurality of electrical heating elements.
 11. A methodaccording to claim 9 further comprising the step of: deactivating theelectrical heating elements when the level of ambient light falls belowa predetermined level of light corresponding to an ambient darkcondition.
 12. A method according to claim 9 further in comprising thesteps of: fitting the heating module on to a support module forproviding electrical power for the heating elements and rapidly heatingthe heating elements at the maximum available heating output until areference temperature is reached, and thereafter switching over to aholding temperature with a reduced heating output.